1. Field of the Invention
This invention relates in general to engines and, in particular, to a rotary engine using detonation waves to initiate fast combustion of a fuel mixture.
2. Description of Prior Art
The reciprocating internal combustion engine which is widely used to transform chemical energy of the fuel into mechanical energy has very low fuel efficiency, usually less than 20 percent of the chemical energy is transformed into mechanical energy. Complex mechanical apparatus is required to transform the reciprocating motion of the piston into the rotary motion of the drive shaft. The sliding friction of the piston in the combustion chamber significantly limits the allowable temperature and pressure in the combustion chamber and thus limits the thermal efficiency of the engine. The combustion of the fuel occurs at ordinary rates. These ordinary rates of combustion result in prolonged heating of the combustion chamber which produces more degradation of the chamber walls per unit volume of fuel burned than when the fuel is burned at a faster rate. This in turn limits the power-to-weight ratio of the engine.
Rotary engines reduce the mechanical complexity by eliminating the need to transform the reciprocating piston motion to rotary motion of the drive shaft. For example, U.S. Pat. Nos. 3,089,307 and 3,804,549 disclose rotory engines in which the rotor has a plurality of circumferentially spaced combustion chambers formed with ducts to exhaust combustion products to provide reaction forces. However, the conventional rotary engines do not provide substantially improved efficiency or power-to-weight ratio over the reciprocating engines because the combustion of fuel occurs at ordinary rates.
The use of intermittent detonation as a thrust producing mechanism has been suggested. See, for example, "Intermittent Detonation as a Thrust Producing Mechanism", J. A. Nicholls et al, Jet Propulsion, May, 1957 and United Kingdon Pat. No. 1,269,123. Both of these references envision detonation apparatus in which the detonation occurs in a plurality of elongated tubular combustion chambers which extend parallel to each other. Complex apparatus is required to transform the linear thrust provided by these devices to the rotary motion required for most applications. This linear combustion chamber arrangement has a problem in providing a smooth continuous output power. A smooth output requires that new fuel mixture be introduced into the combustion chamber at a rate comparable to the very high rate of burn in detonative combustion. Excessive energy is required to introduce the new mixture at the appropriate rate thus reducing the efficiency of the device. Furthermore, the high duty cycle required results in over exposure of the tubular chamber to the combustion process and also a limitation on the speed of the detonation wave because of excessive heat buildup.